(1) Field of the Invention
This invention relates to oil wells, and more particularly to a tubing cleanout tool commonly called a sand pump. Oil field workers who work over or repair producing oil wells are ones having ordinary skill in this art.
(2) Description of the Related Art
Sand pumps and cleanout pumps have been known for many years, e.g., PARR, U.S. Pat. No. 2,237,686, issued in 1941, shows a cleanout pump having a flap valve in the bottom with a piston carrying a ball valve (Also see REYNOLDS, U.S. Pat. Nos. 2,785,756). HARRISON, 4,190,113, issued in 1980, and WILLIAMS ET AL, 4,493,383, issued in 1985, disclose sand pumps particularly adapted to be run upon a drill stem or a tubing string which include a hexagonal mandrel at the top of the barrel so that rotational motion can be imparted to the cleanout tool.
Sand has been a problem in these type tools. One of the primary purposes of the tool is to remove sand from the well as well as other debris. Sand in the tool causes problems. The problem with sand in pumps has been recognized for considerable time, e.g., the patent to HOPKINS ET AL in 1922, U.S. Pat. No. 1,423,935 has a side chamber for an oil well pump to catch the sand. COOK's patent in 1964, U.S. Pat. No. 3,138,215 for a sand pump was concerned that the pump would be locked down by the sand.
There have been many patents issued on cleanout tools of this type. Also, many have been on the market commercially. However, the above indicate some of the problems involved with the sand pump, and also, some of the solutions previous workers have sought. It is noted that HARRISON disclosed a screen below the pump area to prevent large particles from entering the pump section of the cleanout tool.